#include <iostream>
#include <fstream>
#include <vector>
#include <stack>

using namespace std;

ifstream f("ctc.in");
ofstream g("ctc.out");

stack<int>s;
vector<int>graph[105];
vector<int>*sol;
int n, m, from, to, nr, ix[105], llk[105], in=1, viz[105], t=1;

void dfs(int ind)
{
    ix[ind]=llk[ind]=in;
    in++;
    viz[ind]=1;
    s.push(ind);
    for (auto &v:graph[ind])
    {
        if (ix[v]==0)
        {
            dfs(v);
            llk[ind]=min(llk[ind],llk[v]);
        }
        else if (viz[v]==1)
        {
            llk[ind]=min(llk[ind],llk[v]);
        }
    }
    if (llk[ind]==ix[ind])
    {
        while (!s.empty())
        {
            int element=s.top();
            s.pop();
            sol[t].push_back(element);
            viz[element]=0;
            if (ix[element]==llk[element])
            {
                t++;
                break;
            }
        }
    }
}

int main()
{
    f >> n >> m;
    for (int i=1; i<=m; i++)
    {
        f >> from >> to;
        graph[from].push_back(to);
    }
    for (int i=1; i<=n; i++)
    {
        if (ix[i]==0)
        {
            dfs(i);
        }
    }
    g << t-1 << '\n';
    for (int i=1; i<t; i++)
    {
        for (auto &v:sol[i])
        {
            g << v <<' ';
        }
        g << '\n';
    }
    return 0;
}